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  Subjects -> ENGINEERING (Total: 2358 journals)
    - CHEMICAL ENGINEERING (201 journals)
    - CIVIL ENGINEERING (192 journals)
    - ELECTRICAL ENGINEERING (107 journals)
    - ENGINEERING (1240 journals)
    - ENGINEERING MECHANICS AND MATERIALS (394 journals)
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CHEMICAL ENGINEERING (201 journals)                  1 2 | Last

Showing 1 - 200 of 202 Journals sorted alphabetically
AATCC Journal of Research     Full-text available via subscription   (Followers: 8)
ACS Sustainable Chemistry & Engineering     Hybrid Journal   (Followers: 6)
Acta Crystallographica Section B: Structural Science, Crystal Engineering and Materials     Hybrid Journal   (Followers: 6)
Acta Polymerica     Hybrid Journal   (Followers: 9)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Adhesion Adhesives & Sealants     Hybrid Journal   (Followers: 8)
Advanced Chemical Engineering Research     Open Access   (Followers: 37)
Advanced Powder Technology     Hybrid Journal   (Followers: 16)
Advances in Applied Ceramics     Hybrid Journal   (Followers: 5)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 27)
Advances in Chemical Engineering and Science     Open Access   (Followers: 64)
Advances in Polymer Technology     Hybrid Journal   (Followers: 14)
African Journal of Pure and Applied Chemistry     Open Access   (Followers: 7)
American Journal of Polymer Science & Engineering     Open Access  
Annual Review of Analytical Chemistry     Full-text available via subscription   (Followers: 10)
Annual Review of Chemical and Biomolecular Engineering     Full-text available via subscription   (Followers: 12)
Anti-Corrosion Methods and Materials     Hybrid Journal   (Followers: 11)
Applied Petrochemical Research     Open Access   (Followers: 3)
Asia-Pacific Journal of Chemical Engineering     Hybrid Journal   (Followers: 8)
Biochemical Engineering Journal     Hybrid Journal   (Followers: 15)
Biofuel Research Journal     Open Access   (Followers: 4)
Biomass Conversion and Biorefinery     Partially Free   (Followers: 10)
Brazilian Journal of Chemical Engineering     Open Access   (Followers: 4)
Bulletin of Chemical Reaction Engineering & Catalysis     Open Access   (Followers: 2)
Bulletin of the Chemical Society of Ethiopia     Open Access   (Followers: 2)
Carbohydrate Polymers     Hybrid Journal   (Followers: 8)
Catalysts     Open Access   (Followers: 9)
ChemBioEng Reviews     Full-text available via subscription   (Followers: 1)
ChemEngineering     Open Access  
Chemical and Engineering News     Free   (Followers: 17)
Chemical and Materials Engineering     Open Access   (Followers: 18)
Chemical and Petroleum Engineering     Hybrid Journal   (Followers: 13)
Chemical and Process Engineering     Open Access   (Followers: 32)
Chemical and Process Engineering Research     Open Access   (Followers: 29)
Chemical Engineering & Technology     Hybrid Journal   (Followers: 31)
Chemical Engineering and Processing: Process Intensification     Hybrid Journal   (Followers: 16)
Chemical Engineering and Science     Open Access   (Followers: 25)
Chemical Engineering Communications     Hybrid Journal   (Followers: 14)
Chemical Engineering Education     Full-text available via subscription   (Followers: 1)
Chemical Engineering Journal     Hybrid Journal   (Followers: 52)
Chemical Engineering Research and Design     Hybrid Journal   (Followers: 26)
Chemical Engineering Research Bulletin     Open Access   (Followers: 16)
Chemical Engineering Science     Hybrid Journal   (Followers: 28)
Chemical Geology     Hybrid Journal   (Followers: 23)
Chemical Papers     Hybrid Journal   (Followers: 2)
Chemical Product and Process Modeling     Hybrid Journal   (Followers: 4)
Chemical Reviews     Full-text available via subscription   (Followers: 181)
Chemical Society Reviews     Full-text available via subscription   (Followers: 43)
Chemical Technology     Open Access   (Followers: 21)
ChemInform     Hybrid Journal   (Followers: 8)
Chemistry & Industry     Hybrid Journal   (Followers: 6)
Chemistry Central Journal     Open Access   (Followers: 4)
Chemistry of Materials     Full-text available via subscription   (Followers: 243)
Chemometrics and Intelligent Laboratory Systems     Hybrid Journal   (Followers: 14)
ChemSusChem     Hybrid Journal   (Followers: 7)
Chinese Chemical Letters     Full-text available via subscription   (Followers: 2)
Chinese Journal of Chemical Engineering     Full-text available via subscription   (Followers: 4)
Chinese Journal of Chemical Physics     Hybrid Journal   (Followers: 1)
Coke and Chemistry     Hybrid Journal   (Followers: 1)
Coloration Technology     Hybrid Journal   (Followers: 1)
Computational Biology and Chemistry     Hybrid Journal   (Followers: 11)
Computer Aided Chemical Engineering     Full-text available via subscription   (Followers: 1)
Computers & Chemical Engineering     Hybrid Journal   (Followers: 10)
CORROSION     Full-text available via subscription   (Followers: 21)
Corrosion Engineering, Science and Technology     Hybrid Journal   (Followers: 37)
Corrosion Reviews     Hybrid Journal   (Followers: 6)
Crystal Research and Technology     Hybrid Journal   (Followers: 6)
Current Applied Polymer Science     Hybrid Journal   (Followers: 1)
Current Environmental Engineering     Hybrid Journal  
Current Opinion in Chemical Engineering     Open Access   (Followers: 7)
Designed Monomers and Polymers     Open Access   (Followers: 2)
Education for Chemical Engineers     Hybrid Journal   (Followers: 5)
Eksergi     Open Access  
European Polymer Journal     Hybrid Journal   (Followers: 43)
Fibers and Polymers     Full-text available via subscription   (Followers: 6)
Fluorescent Materials     Open Access   (Followers: 1)
Focusing on Modern Food Industry     Open Access   (Followers: 2)
Food and Environment Safety     Open Access  
Frontiers of Chemical Science and Engineering     Hybrid Journal   (Followers: 3)
Gels     Open Access  
Geochemistry International     Hybrid Journal   (Followers: 2)
Handbook of Powder Technology     Full-text available via subscription   (Followers: 6)
Heat Exchangers     Open Access   (Followers: 3)
High Performance Polymers     Hybrid Journal   (Followers: 1)
Hungarian Journal of Industry and Chemistry     Open Access  
Indian Chemical Engineer     Hybrid Journal   (Followers: 5)
Indian Journal of Chemical Technology (IJCT)     Open Access   (Followers: 9)
Indonesian Journal of Chemical Science     Open Access   (Followers: 1)
Industrial & Engineering Chemistry     Full-text available via subscription   (Followers: 11)
Industrial & Engineering Chemistry Research     Full-text available via subscription   (Followers: 21)
Industrial Chemistry Library     Full-text available via subscription   (Followers: 3)
Industrial Gases     Open Access  
Info Chimie Magazine     Full-text available via subscription   (Followers: 3)
International Journal of Chemical Engineering     Open Access   (Followers: 7)
International Journal of Chemical Reactor Engineering     Hybrid Journal   (Followers: 2)
International Journal of Chemical Technology     Open Access   (Followers: 5)
International Journal of Chemoinformatics and Chemical Engineering     Full-text available via subscription   (Followers: 2)
International Journal of Food Science     Open Access   (Followers: 3)
International Journal of Industrial Chemistry     Open Access   (Followers: 1)
International Journal of Polymeric Materials     Hybrid Journal   (Followers: 6)
International Journal of Waste Resources     Open Access   (Followers: 4)
Iranian Journal of Polymer Science and Technology     Open Access   (Followers: 1)
Journal of Chemical Engineering & Process Technology     Open Access   (Followers: 5)
Journal of Applied Crystallography     Hybrid Journal   (Followers: 7)
Journal of Applied Electrochemistry     Hybrid Journal   (Followers: 13)
Journal of Applied Polymer Science     Hybrid Journal   (Followers: 134)
Journal of Applied Science & Process Engineering     Open Access  
Journal of Biomaterials Science, Polymer Edition     Hybrid Journal   (Followers: 9)
Journal of Bioprocess Engineering and Biorefinery     Full-text available via subscription  
Journal of Chemical & Engineering Data     Full-text available via subscription   (Followers: 11)
Journal of Chemical and Biological Interfaces     Full-text available via subscription   (Followers: 1)
Journal of Chemical Ecology     Hybrid Journal   (Followers: 7)
Journal of Chemical Engineering     Open Access   (Followers: 25)
Journal of Chemical Engineering and Materials Science     Open Access   (Followers: 4)
Journal of Chemical Science and Technology     Open Access   (Followers: 6)
Journal of Chemical Sciences     Partially Free   (Followers: 22)
Journal of Chemical Technology & Biotechnology     Hybrid Journal   (Followers: 9)
Journal of Chemical Theory and Computation     Full-text available via subscription   (Followers: 17)
Journal of CO2 Utilization     Hybrid Journal   (Followers: 2)
Journal of Combinatorial Chemistry     Full-text available via subscription   (Followers: 1)
Journal of Crystallization Process and Technology     Open Access   (Followers: 8)
Journal of Environmental Chemical Engineering     Hybrid Journal   (Followers: 7)
Journal of Food Measurement and Characterization     Hybrid Journal  
Journal of Food Processing & Technology     Open Access   (Followers: 1)
Journal of Fuel Chemistry and Technology     Full-text available via subscription   (Followers: 4)
Journal of Geochemical Exploration     Hybrid Journal   (Followers: 1)
Journal of Industrial and Engineering Chemistry     Hybrid Journal   (Followers: 1)
Journal of Information Display     Open Access   (Followers: 1)
Journal of Inorganic and Organometallic Polymers and Materials     Partially Free   (Followers: 10)
Journal of Materials Science and Chemical Engineering     Open Access   (Followers: 1)
Journal of Molecular Catalysis A: Chemical     Hybrid Journal   (Followers: 7)
Journal of Non-Crystalline Solids     Hybrid Journal   (Followers: 8)
Journal of Organic Semiconductors     Open Access   (Followers: 5)
Journal of Physics and Chemistry of Solids     Hybrid Journal   (Followers: 4)
Journal of Polymer and Biopolymer Physics Chemistry     Open Access   (Followers: 7)
Journal of Polymer Engineering     Hybrid Journal   (Followers: 11)
Journal of Polymer Research     Hybrid Journal   (Followers: 7)
Journal of Polymer Science Part C : Polymer Letters     Hybrid Journal   (Followers: 6)
Journal of Polymers     Open Access   (Followers: 6)
Journal of Polymers and the Environment     Hybrid Journal   (Followers: 1)
Journal of Pure and Applied Chemistry Research     Open Access   (Followers: 2)
Journal of the American Chemical Society     Full-text available via subscription   (Followers: 326)
Journal of the Bangladesh Chemical Society     Open Access  
Journal of the Brazilian Chemical Society     Open Access   (Followers: 2)
Journal of The Institution of Engineers (India) : Series E     Hybrid Journal   (Followers: 2)
Journal of the Taiwan Institute of Chemical Engineers     Hybrid Journal   (Followers: 2)
Journal of Water Chemistry and Technology     Hybrid Journal   (Followers: 9)
Jurnal Bahan Alam Terbarukan     Open Access  
Jurnal Inovasi Pendidikan Kimia     Open Access   (Followers: 5)
Jurnal Reaktor     Open Access  
Jurnal Rekayasa Kimia & Lingkungan     Open Access  
Jurnal Teknologi Dan Industri Pangan     Open Access   (Followers: 1)
Konversi     Open Access  
Korean Journal of Chemical Engineering     Hybrid Journal   (Followers: 3)
Main Group Metal Chemistry     Hybrid Journal   (Followers: 2)
Materials Chemistry and Physics     Full-text available via subscription   (Followers: 17)
Materials Science and Applied Chemistry     Open Access  
Materials Sciences and Applied Chemistry     Full-text available via subscription  
Modern Chemistry & Applications     Open Access  
Molecular Imprinting     Open Access  
MRS Communications     Hybrid Journal  
Nanochemistry Research     Open Access  
Nanocontainers     Open Access   (Followers: 1)
Nanofabrication     Open Access  
Noise Control Engineering Journal     Full-text available via subscription   (Followers: 4)
Ochrona Srodowiska i Zasobów Naturalnych : Environmental Protection and Natural Resources     Open Access  
Petroleum Chemistry     Hybrid Journal   (Followers: 1)
Physics and Chemistry of Glasses - European Journal of Glass Science and Technology Part B     Full-text available via subscription   (Followers: 4)
Plasma     Open Access   (Followers: 1)
Plasma Processes and Polymers     Hybrid Journal   (Followers: 3)
Plasmas and Polymers     Hybrid Journal  
Polymer     Hybrid Journal   (Followers: 131)
Polymer Bulletin     Hybrid Journal   (Followers: 8)
Polymer Composites     Hybrid Journal   (Followers: 17)
Polyolefins Journal     Open Access  
Powder Metallurgy Progress     Unknown   (Followers: 1)
Powder Technology     Hybrid Journal   (Followers: 13)
Recent Innovations in Chemical Engineering     Hybrid Journal  
Recyclable Catalysis     Open Access   (Followers: 1)
Research on Chemical Intermediates     Hybrid Journal  
Reviews in Chemical Engineering     Hybrid Journal   (Followers: 5)
Revista Cubana de Química     Open Access  
Revista ION     Open Access  
Revista Mexicana de Ingeniería Química     Open Access  
Rubber Chemistry and Technology     Full-text available via subscription   (Followers: 2)
Russian Chemical Bulletin     Hybrid Journal   (Followers: 2)
Russian Journal of Applied Chemistry     Hybrid Journal   (Followers: 1)
Science and Engineering of Composite Materials     Hybrid Journal   (Followers: 61)
Science of Sintering     Open Access  
Solid Fuel Chemistry     Hybrid Journal  
South African Journal of Chemical Engineering     Open Access   (Followers: 2)
South African Journal of Chemistry     Open Access   (Followers: 2)
Surface Engineering and Applied Electrochemistry     Hybrid Journal   (Followers: 5)
Sustainable Chemical Processes     Open Access   (Followers: 2)
Synthesis Lectures on Chemical Engineering and Biochemical Engineering     Full-text available via subscription  
The Canadian Journal of Chemical Engineering     Hybrid Journal   (Followers: 4)
The Chemical Record     Hybrid Journal   (Followers: 1)
Theoretical Foundations of Chemical Engineering     Hybrid Journal   (Followers: 3)
Transition Metal Chemistry     Hybrid Journal   (Followers: 4)
Transylvanian Review of Systematical and Ecological Research     Open Access  

        1 2 | Last

Journal Cover Chemical Engineering Science
  [SJR: 1.073]   [H-I: 135]   [28 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 0009-2509
   Published by Elsevier Homepage  [3175 journals]
  • Numerical investigation of COD reduction in compact bioreactor with bubble
           plumes
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Khateeb Noor Ul Huda, Kazuya Shimizu, Xiaobo Gong, Shu Takagi
      Water purification using microbubbles has become an important topic, owing to its enhanced mass transfer effect. Therefore, a full 3D numerical model is developed for wastewater purification using microbubbles with bacterial biochemical reactions. Microbubbles are injected into the bioreactor, and the oxygen obtained from microbubble dissolution is used by the bacteria for substrate consumption. This consumption performance may depend on several factors, including physical parameters such as bubble size, column height, and injection type. Optimization of the bioreactor performance based on these parameters would lead to significantly faster purification. In this study, the dependences of these parameters are investigated numerically. The bioreactor model is provided by the mixed Eulerian-Lagrangian formulation for fluid flow and bubble motion tracking in the system. Mass transfer, gas dissolution, and mixing using the Sherwood number approach are employed in this model. Biochemical reactions based on various literatures, including activated sludge models, are used for the current simulation of wastewater purification. Simulations are carried out for an aerobic bacterial system with carbohydrates as the chemical oxygen demand source. The bioreactor height is varied from 1:1 to 4:1 to the base (∼0.1 m), the bubble size is varied from 200 μm to 1 mm, and the central and uniform injection systems are compared. The analysis demonstrates that, for microbubbles with a uniform injection system, a drastic reduction in bioreactor height can be achieved without a performance reduction. An important conclusion is that, for a shorter bioreactor height with 200 μm-microbubble injections, the uniform injection system offers significantly superior performance, while for a longer height with larger (500 μm or 1 mm) bubbles, the central and uniform injections provide nearly the same performance.

      PubDate: 2018-04-16T08:42:27Z
       
  • Hydrodynamic characteristics of particles with different roughness and
           deformability in a liquid fluidized bed
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Gabriela C. Lopes, Xiatao Bi, Norman Epstein, Susan A. Baldwin, John R. Grace
      The effects of particle roughness and deformability on the fluid dynamics of liquid fluidized beds were investigated using a 190.5-mm-diameter column and particles with different surface finish and stiffness. Glass beads and plastic “BBs” coated using different techniques were employed as the rigid particles, while cooked starch pearls (tapioca) and sodium alginate gel beads produced from different gelling solutions served as the deformable particles. The particles were characterized by measuring their densities, diameters, Young’s moduli and coefficients of restitution. Terminal settling velocities were also measured by the free-falling method, and the bed voidages over a wide range of fluid flow rates were estimated from pressure drop measurements along the column height. Correlations for rigid smooth spheres underestimated the single-particle terminal settling velocity for particles with many asperities, especially for the soft spheres. The Richardson-Zaki equation, derived empirically for rigid particles, provided a satisfactory description of the liquid fluidized bed expansion, especially for rigid particles. Although the voidage deviations observed for the soft particles were less than 10%, the fluidization behavior of these particles was affected much more by the particle Stokes number than for rigid spheres. Though there is evidence in the literature that particle surface roughness is responsible for the deviation from predicted bed expansion in the fluidization of bioparticles, results presented in this study indicate that the mechanical properties of these soft particles can also be a major influencing factor.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Prediction of degree of impregnation in thermoplastic unidirectional
           carbon fiber prepreg by multi-scale computational fluid dynamics
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Son Ich Ngo, Young-Il Lim, Moon-Heui Hahn, Jaeho Jung
      A multi-scale simulation approach was proposed to predict the degree of impregnation (DoI) in thermoplastic unidirectional carbon fiber prepreg (UD-CFP). The multi-scale approach included a two-dimensional (2D) micro-scale computational fluid dynamics (CFD) in a representative elementary volume (REV) of carbon fiber (CF) tow, a 3D macro-scale CFD of an entire impregnation die with 15 sliding CF tows, and a process-scale simulation assembling data from the micro- and macro-scale CFDs. In the macro-scale steady-state CFD, thermoplastic resin injection and CF tow insertion were considered for an impregnation die 10 cm in width. In the micro-scale transient CFD, impregnation mechanisms of resin into CF filaments 7 μm in diameter were identified in terms of surface coverage, capillary permeation, and penetration through CF filaments. The DoI as a function of pressure and time was obtained from the micro-scale CFD within a range of pressures found in the macro-scale CFD. In the process-scale simulation, the cumulative DoI of the 15 tows was predicted along the impregnation die length with the aid of the micro- and macro-scale CFD results. Combining the multi-scale models gives a potential to predict the uniformity of the transverse resin amount in the final UD-CFP product.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Current density distributions in polymer electrolyte fuel cells: A tool
           for characterisation of gas distribution in the cell and its state of
           health
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): M. Belhadj, A. Aquino, J. Heng, S. Kmiotek, S. Raël, C. Bonnet, F. Lapicque
      Distributions of current density (cd) in a 100 cm2 single polymer fuel cell have been measured, leading to a 12 × 12 data array. For a freshly matured MEA, the dimensionless distributions have been shown to be of moderate uniformity, whatever the cell current, with average deviations of the dimensionless cd in the range 0.16–0.25 (i.e. cd measured deviated from 16 to 25% from the expected value). More thorough examination of the data acquired showed that the non-uniformity is likely due to maldistribution of the gas in the 23 parallel channels of the multiple serpentine pattern of the commercial bipolar plates. For the sake of comparison, the MEA – including the two GDL was submitted to ageing with a standard cycling protocol (FC_DLC) emulating transportation conditions for 500 h. Characterisation of the cell state of health afterwards revealed visible degradation of the GDL, whereas the catalytic layer and the membrane were little affected. In the aged cell, distributions were shown to be far more non-uniform, with deviations ranging from 0.30 to 0.50: the current distributions were then depending on the cell current density. Presumably, due to the GDL ageing, liquid water produced at high cd, could not be removed efficiently, resulting in very low cd’s near the outlet.

      PubDate: 2018-04-16T08:42:27Z
       
  • Removal of gas bubbles from highly viscous non-Newtonian fluids using
           controlled vibration
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Xiaobin Zhan, Yu He, Baojun Shen, Zhibin Sun, Tielin Shi, Xiwen Li
      Formation of gas bubbles is normal and practically inevitable when fluids are agitated or flow in open containers. The unwanted gas bubbles will damage the product quality, and they are very difficult to be removed from highly viscous fluids. In this paper, the effectiveness of vibration degassing for highly viscous non-Newtonian fluids is investigated using volume of fluid (VOF) model coupled with continuous surface force (CSF) model. The motions of gas bubbles in liquid under vibration are simulated and the effects of various rheological parameters as well as vibration parameters on the degassing rate are studied. The results show that the shear thinning (or thickening) induced by vibration is responsible for the enhancement (or retardation) of degassing rate for non-Newtonian fluids. The more pronounced the non-Newtonian behaviors of fluids are, the greater the effects of vibration on the degassing rate are. The degassing rate is governed by the vibration amplitude and frequency of vibration. However, high frequency or large amplitude vibration may intensify air entrapment and bring new gas bubbles into fluids. Thus, the feasible region of vibration degassing in which the vibration frequency and amplitude don’t cause new gas bubbles are further studied. The vibration degassing technology has the added advantage that it does not use intrusive devices to container, nor does it limit the container structure or shape, and thus will find wide applications in laboratory and industrial fields.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Modulation of turbulent flow field in an oscillating grid system owing to
           single bubble rise
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Mohammad Mainul Hoque, Subhasish Mitra, Geoffrey M. Evans, Mayur J. Sathe, Jyeshtharaj B. Joshi
      Modulation of turbulent flow in an oscillating grid system due to controlled release of a bubble train was experimentally investigated using particle image velocimetry (PIV) technique wherein flow field modulation was reported in single bubble resolved manner. The bubble diameter was varied in the range ∼2.70 to 3.52 mm (∼26 to 34 times the single-phase Kolmogorov scale, and ∼1.05 to 1.35 times the single-phase integral length scale). The two-dimensional (2D) instantaneous velocity fields were obtained for both single–phase and bubble train cases at grid Reynolds numbers (Reg ) ranging from 1080 to 10,800. The modulation of single-phase turbulence due to bubble was analysed based on the turbulence intensity, isotropy ratio (IR), length scales, specific energy dissipation rates and energy spectra. The single-phase turbulence fluctuating velocity increased ∼5–76% in the inertial subrange region in the presence of bubbles. Presence of bubbles also led to enhancement in the flow field isotropy ratio due to upward acting buoyancy force. It was noted that at high Reg (6480–10800), the IR value of the flow was found to be more dependent on the grid Reynolds number compared with bubble diameter. The integral length scale of the single-phase flow decreased following a power law dependency over the Reg . It was found that the specific energy dissipation rate of single–phase flow increased with an increase in bubble diameter. The energy spectra exhibited a slope less steep than −5/3 which indicates the additional turbulence production by the bubbles in the inertial subrange region. Energy transfer augmentation from large scale to small scale due to bubble was explianed by the dissipative spectrum which showed reduction of the energy in the small scale and an enhancement of the energy in both large scale and inertial subrange.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Evaluating lower flammability limit of flammable mixtures using threshold
           temperature approach
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Chan-Cheng Chen, Shang-Hao Liu, Xiaoyan Kang
      A flammable gas could be ignited only if its concentration in air is over a threshold concentration, which is known as the lower flammability limit (LFL). Therefore, predicting LFLs of flammable gases is indispensable for safely handling such flammable gases. The Le Chatelier’s mixing rule for the LFL is the prevailing method for estimating the LFLs of mixtures with multiple flammable components. In this work, a novel derivation for this rule is proposed based on the threshold temperature concept. It is found that the important assumption required to reach this mixing rule is that the adiabatic flame temperature rises at LFL are approximately the same for each flammable component. As the adiabatic flame temperature rise is in a sense the required energy gap to initiate a combustion, it should not change while adding/removing inert gas into/from the system. Therefore, it is also the required perquisite to predict the LFLs of inertized mixture or the LFLs in oxygen atmosphere.

      PubDate: 2018-04-16T08:42:27Z
       
  • Preparation and characterization of mixed matrix membranes based on
           Matrimid/PVDF blend and MIL-101(Cr) as filler for CO2/CH4 separation
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Hajar Rajati, Amir H. Navarchian, Shahram Tangestaninejad
      In this work, the effect of addition of MIL-101(Cr) metal–organic framework (MOF) and poly(vinylidene fluoride) (PVDF) on physicochemical, morphological and CO2/CH4 separation properties of Matrimid was investigated. MIL-101(Cr) micron-sized particles were synthesized and dispersed as filler in Matrimid/PVDF blended matrix so that a mixed matrix membrane (MMM) was formed. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis were used to characterize the MIL-101(Cr) particles. The Matrimid/PVDF blend membranes were investigated by optical microscopy (OM), differential scanning calorimetry (DSC) and Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectrophotometry. SEM images were employed to characterize the morphology of membranes. Single-gas permeability measurements for prepared membranes were performed and the results showed improvement in gas permeability of fabricated membranes in comparison with the neat Matrimid membrane. The best performance of blend membrane was obtained with 3 wt% of PVDF, leading to increase 29% and 23% in CO2 permeability and CO2/CH4 selectivity, respectively, as compared to the pristine Matrimid. Furthermore, the gas permeability and CO2/CH4 selectivity were improved simultaneously for Matrimid/PVDF/MIL-101 membrane. The CO2 permeability in this membrane increased 102% and 58%, and the ideal selectivity increased 77% and 45% as compared to the neat Matrimid and Matrimid/PVDF(97/3) membranes, respectively.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Design of flexible multiperiod heat exchanger networks with
           debottlenecking in subperiods
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Lixia Kang, Yongzhong Liu
      In order to accommodate potential fluctuations of uncertain parameters, a systematic three-stage method for the design of flexible multiperiod heat exchanger networks (HENs) is proposed, which satisfies not only the requirement of the multiperiod operation but also the flexibility of the subperiod operation. In the first stage, an initial multiperiod HEN is constructed based on the synthesis of the single period HEN. In the second stage, the structure and heat transfer area arrangement of the initial multiperiod HEN are modified and optimized by considering both the multiperiod operational characteristics and the subperiod operational flexibilities. In the third stage, the flexibilities of the modified multiperiod HEN in each subperiod are examined and improved by solving a subperiod debottlenecking model. A case study of a HEN in a vacuum gas oil hydrotreating unit is carried out to illustrate the application of the proposed method. Results indicate that the heat transfer areas and total annual cost of the multiperiod HEN will be underestimated if the parametric fluctuations in subperiods are neglected. A cost-effective multiperiod HEN with sufficient flexibility in subperiods can be obtained by using the proposed method when the parametric fluctuations are taken into consideration.

      PubDate: 2018-04-16T08:42:27Z
       
  • General correlation for maximum heat transfer to surfaces submerged in
           gas-fluidized beds
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Mirza M. Shah
      A general correlation is presented for predicting maximum heat transfer coefficient for surfaces submerged in gas-fluidized beds. It has been verified with data for horizontal and vertical cylinders and spheres in beds of a wide variety of particles and gases. The gases include air, cryogens, methane, CO2, ammonia, and R-12. The rage of parameters includes: heat transfer surface diameter 0.05–220 mm, particle diameter 31–15000 µm, pressure 0.026–0.95 MPa, and temperature 13–1028 °C. The 363 data points from 53 sources are predicted with a mean absolute deviation of 16.2%. Several other correlations were also compared to the same data but had much larger deviations.

      PubDate: 2018-04-16T08:42:27Z
       
  • Experimental and model studies of p–nitrophenol and phenol separation in
           the bulk liquid membrane with the application of bond–graph method
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Piotr Szczepański
      A new method has been developed to describe the transport and separation of phenolic compounds in the agitated bulk liquid membrane system (ABLM). The pseudo-thermodynamic network analysis was applied to simulate the solution–diffusion transport of phenol (PH) and p–nitrophenol (PNP) with a fast neutralization reaction in the stripping solution. The comparison of the experimental results in the system: PH, PNP aq. soln. (pH = 2) cyclohexane NaOH soln. (pH = 10) with the results of calculations indicate that the model can be successfully applied for prediction of the time dependent PH/PNP separation characteristics of the ABLM system under study. It was found that the separation PH/PNP factor attaining 50 was observed by experiments and calculations. The liquid membrane system can be considered as useful for phenol removal from the mixture with PNP or PNP cleaning as the reagent for its specific applications.

      PubDate: 2018-04-16T08:42:27Z
       
  • General performance evaluation charts and effectiveness correlations for
           the design of thermocline heat storage system
    • Abstract: Publication date: 10 August 2018
      Source:Chemical Engineering Science, Volume 185
      Author(s): Zhao Ma, Ming-Jia Li, Wei-Wei Yang, Ya-Ling He
      One-tank molten salt thermocline heat storage system can reduce capital cost due to the use of cheap heat storage materials as compared with two-tank molten salt heat storage system. In order to develop a convenient method for the evaluation and design of the one-tank thermocline heat storage system, the idea of effectiveness-number of transfer unit method (ε-NTU) for heat exchanger design was employed in which three dimensionless design parameters are defined including the ratio between overall thermal conductance and the total thermal capacity of heat transfer fluid flowing through the system during discharging process (i.e., NTU), the ratio between thermal capacity of solid particles and total thermal capacity of heat transfer fluid through the system during the discharging process (i.e., C s ∗), the ratio between overall thermal conductance in the charging process and that in the discharging process (i.e., (hA)∗). A transient one-dimensional dispersion-concentric model is then applied to study the effects of three dimensionless parameters on the effectiveness of one-tank system. It is shown that the effectiveness of the one-tank thermocline heat storage system is closely related to NTU, C s ∗ and (hA)∗. Based on the simulated results, general performance evaluation charts and the related effectiveness correlations are also proposed for evaluation and design of the one-tank system. Moreover, the proposed effectiveness correlations are finally applied in the design of a one-tank molten salt thermocline heat storage system in a 50 MWe CSP plant.

      PubDate: 2018-04-16T08:42:27Z
       
  • Optimization of oxygen transport within a tissue engineered vascular graft
           model using embedded micro-channels inspired by vasa vasorum
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): M. Soltani, Mohammad Amin Maleki, Amir Hossein Kaboodrangi, Bobak Mosadegh
      Tissue Engineered Vascular Graft (TEVG) is a promising treatment for cardiovascular diseases because of its potential for repair and long-term patency. However, the quality and preparation time to achieve a mature TEVG has limited its use in clinical settings. Both of these factors can be improved by effectively growing TEVGs with a uniform and high cell density, which is currently limited due to the diffusion limit of oxygen and nutrients. In this paper we propose a novel optimized microchannel geometry in TEVG wall model that facilitates uniform oxygen transport within a simulated TEVG with high cell density. In order to model the oxygen mass transport incompressible Navier-Stokes, convection, and diffusion equations were solved numerically. Furthermore, to model oxygen consumption in the graft domain, Michaelis-Menten kinetics were coupled with the oxygen diffusion equation. Finally, an optimized model was yielded such that nearly four times the cell density can be sustained by using the proposed microchannels design compared to a simulated TEVGs with a solid wall. In addition, to minimize the oxygen gradient along the graft, multiple segments are added to microchannels and their locations along the microchannels are optimized. We believe these simulated results can help guide the design and fabrication of optimized TEVGs.

      PubDate: 2018-04-16T08:42:27Z
       
  • Development and validation of an enhanced filtered drag model for
           simulating gas-solid fluidization of Geldart A particles in all flow
           regimes
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Xi Gao, Tingwen Li, Avik Sarkar, Liqiang Lu, William A. Rogers
      Coarse-grid two-fluid simulation of gas-solid fluidized bed reactors based on the kinetic theory of granular flow exhibits a significant dependence on drag models, especially for Geldart A particles. Many drag models are available in the literature, which have been reported to work for different systems. This study focused on the evaluation of an enhanced filtered drag model along with other different drag models derived from different methods for three-dimensional two-fluid model simulations of gas-solid fluidized beds of Geldart A particles covering a broad range of fluidization regimes, including bubbling fluidization, turbulent fluidization, fast fluidization, and dilute phase transport regimes. Eight drag models were selected, which included five heterogeneous drag models and three homogeneous drag models. Comparison with the available experimental data demonstrates the need for modification of homogeneous drag models to account for the effect of mesoscale structures (i.e., bubbles and clusters). The enhanced filtered drag model and energy-minimization multi-scale (EMMS) drag models were found to achieve superior predictions in all fluidization regimes, while the other drag models were only capable of predicting certain fluidization regimes. The results of this work provide a guideline for choosing appropriate drag models for simulating Geldart A particles and suggestions on developing more reliable and general drag models applicable in all flow regimes.

      PubDate: 2018-04-16T08:42:27Z
       
  • Sedimentation and consolidation of different density aggregates formed by
           polymer-bridging flocculation
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): F.A. Benn, P.D. Fawell, J. Halewood, P.J. Austin, A.D. Costine, W.G. Jones, N.S. Francis, D.C. Druett, D. Lester
      There are numerous models of sedimentation in fine particle suspensions, derived from or validated with physical measurements. Such models could be applied to optimise and control gravity thickeners used for solid-liquid separation in mineral processing. However, these applications rely upon particle bridging by high molecular weight polymers to form large, low density and fragile aggregates. The evolution and refinement of sedimentation modelling for flocculated systems is restricted by a lack of meaningful control of flocculation conditions and inadequate detail in the experimental sedimentation data used for validation. To address this problem, an experimental system was built to give high fidelity sedimentation data, its use demonstrated for flocculated calcium carbonate suspensions. Turbulent pipe flow flocculation offers tight control of dosage, mean shear rate and reaction time, with aggregate size monitored in-line. The pipe discharges into the base of a wide (190 mm ID) transparent column for which the contents can be isolated, with mudlines then determined from image capture and bed profiles by γ-attenuation. The use of wide columns minimised wall effects that can limit consolidation, while simultaneous efforts to maximise measurement reproducibility and sensitivity led to a greater ability to distinguish subtle impacts from variations in flocculation. Duplicate columns with detachable lower sections enable direct vane yield stress measurement at known bed depths and thereby plots of yield stress vs. solids fraction. Modelling of such data will be described in subsequent publications, with the present study focusing on key experimental requirements and limitations, the form of data outputs and insights into flocculation impacts. For the latter, off-line determination of individual aggregate settling rate vs. size after bed sampling confirmed that higher solids volume fractions low within beds occurred through removal of both inter- and intra-aggregate liquor, i.e. there is a contribution from aggregate densification. Bed profiles and yield stress responses also indicate flocculant functional chemistry can alter how aggregation limits the solids volume fractions attained.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Investigation of fluidized bed agglomerate growth process using
           simulations and SEM-EDX characterization of laboratory-generated
           agglomerates
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Aditi B. Khadilkar, Peter L. Rozelle, Sarma V. Pisupati
      This study elucidates the sequential progression of agglomerate growth in fluidized beds through an investigation of physics and chemistry of particle-particle interaction. In fluidized bed gasification and combustion systems, agglomeration occurs by sticking of ash particles that are wetted by slag-liquid. Penn State has developed an agglomeration modeling methodology that considers non-uniform temperature, gaseous atmosphere and heterogeneity in ash chemical composition to predict slag-liquid formation and agglomerate growth rate. Simulations performed on three high rank coals with a consideration of these heterogeneous conditions, along with a microscopic (SEM) particle-level analysis of agglomerates facilitated an understanding of steps involved in their formation. The results of this study indicated that agglomerate growth in fluidized bed systems is initiated at the particle-level by low-melting components rich in iron- and calcium-based minerals. Agglomeration can begin at lower temperatures than the fluidized bed operating temperatures of 850 °C and the severity of agglomerate growth issues can be identified based on the slag-liquid level in the system. Understanding the stages involved in the process of agglomerate growth discussed in this paper can help develop early detection methods and mitigation strategies.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Study of the organic solvent template double emulsions for porous
           microspheres production with adjustable structures
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Chao Dong, Zhiyi Li, Fengxia Liu, Wei Wei, Xiaojuan Wang, Zhijun Liu
      In this study, the method of Hansen solubility parameters was applied to identify a solvent substitution less toxic than dichloromethane used in a microencapsulation process. A theoretical approach was developed to investigate the influence of solvent type on water permeation across the solvent film in w/o/w template double emulsions. Analysis showed that water solubility in the solvent was a key factor in deciding water permeability across the solvent film, which could vary significantly with different solvents. Besides high water permeability, experiments showed that dichloromethane and ethyl acetate films in double emulsion also featured very low film robustness due to their high water permeability and poor film robustness. To improve film robustness, the influence of polymer and surfactant concentration in the film phase was studied. Results showed that increased viscosity and non-Newtonian conversion induced by polymers dissolved in the film phase could significantly improve the stability of the template double emulsion; the addition of hydrophobic surfactant Span 80 in the film phase significantly destabilized double emulsion with twofold effects: at low concentration water permeation was promoted while at high concentration deformation and breakup of the oil film were facilitated. Further study showed that different internal structures, i.e., microspheres of single- and multi-compartments, could be effectively tailored by employing the water permeation characteristics as predicted by the permeation model. The large cavity of the hollow single-compartment microspheres makes them particularly suitable as delivery vehicle systems.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • New invariances for chemical reactions from Scaled Incremental Conversion
           (SIC)
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): P. Daniel Branco, Gregory S. Yablonsky, Guy B. Marin, Denis Constales
      For the two-step chemical reaction A ⇄ B ⇄ C, invariant dependences of a new type have been found. These invariants relate concentration dependences which are started from the single component (single-component-dependences). For constructing the invariants, a three-stage procedure is used: 1. Scaled Incremental Conversion (SIC), χ, is determined for any substance as χ = X ( t ) - X o X eq - X o , where Xeq and Xo are equilibrium and initial concentrations for any substance, A, B, or C, respectively; X(t) is the concentration at any moment of time. 2. Differences of SIC terms Δχ are determined for different pairs of substances. SIC terms are calculated in experiments with symmetrical initial conditions. 3. A generating function of invariants is constructed which produces invariants as ratios of different Δχ. These ratios remain constant at any time during the non-steady-state reaction. It is demonstrated that the variety of invariants obtained depends on the initial conditions used in the procedure. Explicit analytical expressions have been found assuming the same initial conditions, two, and three different initial conditions, respectively. All invariants are functions of three independent parameters which are ratios of kinetic coefficients. Two of them are equilibrium reaction constants, and the third one is the ratio of kinetic coefficients belonging to different reactions.

      PubDate: 2018-04-16T08:42:27Z
       
  • Heterogeneous catalysis in microreactors with nanofluids for fine
           chemicals syntheses: Benzylation of toluene with benzyl chloride over
           silica-immobilized FeCl3 catalyst
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Xin Pu, Yuanhai Su
      A novel strategy for a heterogeneous benzylation reaction conducted in a capillary microreactor was proposed. Silica-immobilized FeCl3 nanocatalysts were dispersed in benzyl chloride to form a nanofluid, and then were applied for the benzylation of toluene with benzyl chloride to produce monobenzyl toluene and dibenzyl toluene. The effects of various factors, such as reaction temperature, catalyst composition and residence time on the reaction performance were systematically evaluated. The benzyl chloride conversion could reach 99.2% with the 10%FeCl3-SiO2 catalyst under optimal conditions. Both internal effectiveness factor and external effectiveness factor were estimated to explore the influence of internal diffusion and external diffusion on the reaction performance and to reveal the rate-controlling step during the continuous-flow synthesis. Furthermore, the carbenium ions mechanism was applied to elaborate this heterogeneous benzylation reaction. The nanocatalysts could be regenerated and reused for three times with a high catalytic activity (conversion of benzyl chloride >70%), showing great application potential of this nanofluid catalysis protocol on chemical transformations for fine chemicals syntheses.

      PubDate: 2018-04-16T08:42:27Z
       
  • Constituent solubility and dissolution in a CuCl-HCl-H2O ternary system
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Ofelia A. Jianu, Zhaolin Wang, Greg F. Naterer, Marc A. Rosen
      The copper-chlorine (Cu-Cl) cycle has significantly lower temperature requirements than most other cycles of thermochemical hydrogen production. The cycle involves multiple steps which include multiphase transport processes. Thermodynamic equilibrium of ternary mixtures in the Cu-Cl cycle have important effects on the transport processes. A ternary system consisting of cuprous chloride (CuCl), hydrochloric acid (HCl) and water exists in different variations of the Cu-Cl cycle. In this paper, new correlations are developed for the solubility of the ternary system, which are essential to providing accurate boundary conditions for the transport processes. This paper examines these multi-constituent transport processes and the corresponding constituent solubilities. A new semi-empirical formulation is presented for the solubility of the ternary system. Results are given and discussed.

      PubDate: 2018-04-16T08:42:27Z
       
  • Oxygen reduction reaction on Pt(1 1 1), Pt(2 2 1), and
           Ni/Au1Pt3(2 2 1) surfaces: Probing scaling relationships of reaction
           energetics and interfacial composition
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Hao Wang, Wei An, Xiaoyang Liu, C. Heath Turner
      In this work, we investigate the oxygen reduction reaction (ORR) on Pt(1 1 1), Pt(2 2 1), and Ni/Au1Pt3(2 2 1) surfaces using periodic density functional theory (DFT) calculations augmented with kinetic Monte Carlo (KMC) simulations. In the DFT calculations, both a uniform electric field and an implicit solvent were employed to quantify the changes in the ORR energetics. Based on the DFT values and the reaction mechanism of ORR, KMC simulations were performed to predict the current densities and the surface populations as a function of the electrode potential on the different catalyst surfaces. These results were compared to an ORR model with energetics approximated using scaling relationships. The two approaches for obtaining energetic parameters yield different KMC-predicted polarization curves. An analysis of the surface species concentrations on Pt(1 1 1), Pt(2 2 1), and Ni/Au1Pt3(2 2 1) indicates dramatic concentration variations at different potentials. Direct neighbor-neighbor interactions on the surface were also tested, but they were found to only moderately influence the surface species concentrations, and they led to imperceptible changes in the predicted current densities. Overall, we predict that an alloy surface of Ni/Au1Pt3(2 2 1) can significantly shift the onset potential of the polarization curve to higher potentials, providing guidance for future electrocatalyst design.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • A solvent ‘squeezing’ strategy to graft ethylenediamine on Cu3(BTC)2
           for highly efficient CO2/CO separation
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Ruiqin Zhong, Xiaofeng Yu, Wei Meng, Songbai Han, Jia Liu, Yunxing Ye, Changyu Sun, Guangjin Chen, Ruqiang Zou
      Highly efficient separation of residual carbon dioxide (CO2) from syngas, mainly composed of carbon monoxide (CO) and hydrogen (H2), could not only make its utilization more energetically efficient but also avoid catalysts poisoning in some industrial applications. In the attempts to address this issue, it is acknowledged that CO2/CO separation is the vital step since H2 is a nonpolar molecules, difficult to be polarized and could be easily separated from CO2. Herein, we report a novel strategy to graft basic ethylenediamine (ED) molecules onto porous metal–organic frameworks (MOFs) as solid adsorbents for CO2/CO separation via solvent ‘squeezing’ approach, in which Cu3(BTC)2 (BTC = 1,3,5-benzenetricarboxylate) MOF was employed as the pristine MOF. Surprisingly, the ED-grafted Cu3(BTC)2 shows unprecedented enhancement of CO2/CO selectivity of 226% at 273 K and 861% at 298 K, respectively, in comparison with the solvent-free Cu3(BTC)2. Moreover, despite the large isosteric heats of adsorption of CO2 on the ED-grafted Cu3(BTC)2, it could be easily regenerated at moderate temperature. This work provides an efficient and facile method to functionalize MOFs for CO2 capture.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Solvent similarity analysis−from qualitative to quantitative
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Yueqiang Zhao, Weiwei Liu, Jing Zhu, Xiaoqin Pei
      We put forward a new expression of similarity between solute and solvent in terms of the cohesive energy for unlike molecules, which provides a quantitative measure of the principle that ‘like dissolves like’. The investigation results indicate that as Vr (volume ratio) and SHSPR (the Square of Hansen Solubility Parameter Ratio) are far larger than unity (Vr  ≫ 1, SHSPR ≫ 1), the similarity degree between solute and solvent is dominate by difference in molecular structure (size and interaction energy); as SHSPR approaches unity (SHSPR → 1), the similarity degree is irrelative with molecular size, and it depends only on its deviation from ideal solution (positive or negative deviation). Its applications in water−solvent miscibility analysis, appropriate solvent selection for polymers and chemical products purification (liquid-liquid extraction and re-crystallization) have been verified with successful results.

      PubDate: 2018-04-16T08:42:27Z
       
  • Evaluation of a dense skin hollow fiber gas-liquid membrane contactor for
           high pressure removal of CO2 from syngas using Selexol as the absorbent
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Bouchra Belaissaoui, Eric Favre
      Integrated Gasification Combined Cycle (IGCC) technologies involve the processing of synthesis gas (syngas) produced by carbonaceous fuels gasification. CO2 removal from syngas is a key requirement for combined CO2 capture and hydrogen production in IGCC power plant processes for both power generation and greenhouse-gas emission mitigation. Conventional absorption in packed columns using pressurized physical solvents such as Dimethyl Ether of Polyethylene Glycol (DEPG) (Selexol™) is commonly used for this application. In this work, a dense skin hollow fiber membrane contactor (HFMC) based process for CO2 absorption and desorption using Selexol as a physical absorbent is investigated by simulation and compared to the conventional process. The ability of dense membranes to withstand high transmembrane pressure differentials allows the absorbent to circulate in a closed loop system at a fixed pressure set independently of the syngas pressure. Differing from the conventional process, neither absorbent depressurization before the desorber nor absorbent recompression before the absorber are needed. Under the investigated operating conditions wherein we used polydimetylsiloxane (PDMS), one of the most gas permeable polymeric membrane materials available, this process allowed for recovery of up to 94.6% of CO2, with CO2 and H2 purity of 92.4% and 96.6% respectively. The corresponding energy requirement for the absorption and desorption loop was of 0.19 MJel/kg CO2 which is approximately two times lower than that reported in the literature under comparable gas inlet conditions and separation specifications using packed columns. Without flash recovery, the corresponding H2 loss was of 4.8%. The overall mass transfer coefficient was of 1.2 · 10−5 m/s and 6.8 · 10−6 m/s in the absorber and desorber respectively. Membrane mass transfer lower or comparable to that of the absorbent combined with higher CO2/H2 membrane selectivity is required for H2 loss decrease. Lower H2 loss is achieved at the expense of increased contactor size and liquid energy pumping energy. Finally, perspectives for process optimization are proposed.

      PubDate: 2018-04-16T08:42:27Z
       
  • Novel solvent exchange distillation column
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Farhad Fazlollahi, Phillip C. Wankat
      Solvent exchange or solvent swap is commonly used in production of complex organic molecules when the next processing step requires that the solute be dissolved in a different solvent. The current methods for solvent exchange, batch distillation and diafiltration, also produce a waste stream containing a mixture of the feed and chasing solvents that must be separated, usually by distillation. The results obtained from an Aspen Plus model of the new exchange column are compared with constant volume batch distillation simulations for both still pot and still pot plus column systems. The new solvent exchange column reduces the amount of the waste stream, and when the feed solvent is the more volatile solvent the exchange column can often be designed to produce feed solvent at the desired purity; thus, eliminating the need for an additional distillation column to separate the two solvents. When the initial solvent is the less volatile component, the new exchange column will often be competitive with constant volume diafiltration which is currently used.

      PubDate: 2018-04-16T08:42:27Z
       
  • Cubic equations of state extended to confined fluids: New mixing rules and
           extension to spherical pores
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Gabriel D. Barbosa, Michelle L. D'Lima, Shaden M.H. Daghash, Marcelo Castier, Frederico W. Tavares, Leonardo Travalloni
      The thermodynamic behavior of fluids confined in nanopores is highly influenced by the interaction between fluid molecules and pore walls. The most accurate approaches for modeling confined fluids are too computationally demanding for practical engineering requirements, such as process simulation. Thus, several efforts have been made to develop analytical equations of state suitable for confined fluids. The scope of this work consists of a modification to our previous modeling of fluid confinement in cylindrical pores based on cubic equations of state. By using new, more explicit mixing rules, a more consistent description of confined mixtures is obtained. Additionally, this modeling approach is extended to spherical pores. The proposed models displayed good predictive performance for the adsorption of binary and ternary mixtures, based on pure fluid adsorption data only, with an improvement relative to the previous modeling. It is shown that the adopted pore geometry can significantly affect the model performance.

      PubDate: 2018-04-16T08:42:27Z
       
  • Molecular dynamics simulation of the aggregation phenomenon in the late
           stages of silica materials preparation
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Reza Gholizadeh, Yujun Wang
      Molecular dynamics simulations are employed to investigate the aggregation behavior at the late stages of silica production in a colloidal solution to find new insights into the structures and dynamics of the produced aggregates and pores. The implemented theoretical investigations used the Amorphous cell and Forcite modules, and Dreiding force field of Materials Studio package. The key thermodynamic parameters, mean squared displacements, and radial distribution functions were calculated. Results revealed that aggregation occurred in the late stages due to the negative value of Gibbs free energy. Diameters of the generated “aggregates and pores” continuously increased while the number of “aggregates and pores” first increased and then decreased. Furthermore, the volume of pores first rose and then fell as the reaction proceeded. Variations of reactant numbers had the noticeable influence on the pores and aggregates topologies. The number of aggregates and pores had an upward trend while their diameters slightly reduced when more effective molecules were involved in the aggregation process. In addition, the shape of the aggregates examined and found that the predominant shapes of the aggregates were spherical.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Prediction of ionic liquids viscosity at variable temperatures and
           pressures
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Fangyou Yan, Wensi He, Qingzhu Jia, Qiang Wang, Shuqian Xia, Peisheng Ma
      The viscosity of ionic liquids (ILs) plays an important role in the chemical industry, material science and environmental science. This work presents a temperature- and pressure-dependent (η-T-P) model based on the norm indices for describing the viscosity of ILs. While the parameters for the temperature and pressure dependence of the viscosity have been generally set as constants in previous work, they are adjusted based on the molecular structures in the η-T-P model. Because ILs consist of only cations and anions, the norm indices are derived from cations and anions, respectively. However, the close connection between the interaction of the cations and anions and IL viscosity cannot be neglected; therefore, another set of norms is further deduced to represent the cation–anion interaction. The η-T-P model is developed using 349 ILs (3228 data points) in the temperature range of 253.15–573.00 K and the pressure range of 0.06–300.00 MPa. Consequently, a η-T-P model is derived with convincing results, as evaluated by the following statistical parameters: the squared correlation coefficient (R 2), Fisher significance (F) and the overall average absolute relative deviation (AARD), which are 0.964, 1809 and 4.62%, respectively.

      PubDate: 2018-04-16T08:42:27Z
       
  • Micromixing performance and the modeling of a confined impinging jet
           reactor/high speed disperser
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Ao Nie, Zhengming Gao, Lin Xue, Ziqi Cai, Geoffrey M. Evans, Archie Eaglesham
      In order to get a better micromixing performance, an intensification reactor that couples a confined impinging jet reactor and high speed disperser (CIJR-HSD) was designed. The influences of operating and structural parameters on the micromixing performance were investigated by using the iodide-iodate reaction system. The results showed that the segregation index decreased with the increase of both the rotational speed and the number of rotors; whilst there was little influence due to both inlet flow rate and the presence of packing. The coupling distance between the centre of the CIJR and the first rotor of the HSD also had a non-negligible effect on segregation index. The micromixing time was determined by the Engulfment model, and could also be evaluated by the energy dissipation model based on fluid energy transformation. It was found that the micromixing time for the CIJR-HSD device was in the range of 0.1–0.3 ms, while that for a single CIJR was in the range of 0.35–0.5 ms.

      PubDate: 2018-04-16T08:42:27Z
       
  • Investigation and prediction of severe slugging frequency in
           pipeline-riser systems
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Hongliang Zhou, Liejin Guo, Han Yan, Shicai Kuang
      Severe slugging is one of the flow assurance concerns in oil and gas industry because of the undesired fluctuations of pressure and flow rates in the system. Knowledge of severe slugging frequency is essential for the receiving facility design. However, unlike the considerable investigations of normal slug frequency in horizontal and inclined pipes, little work has been done to predict severe slugging frequency. In this work, an experimental study of air-water two-phase flow was conducted in a long pipeline-riser system. According to the riser pressure drop signals and the power spectral density (PSD) distributions, flow patterns were classified into classical severe slugging, transitional severe slugging, oscillating flow and stable flow. The effect of riser-top choking on classical and transitional severe slugging frequency were analyzed. Based on a broad range experimental database from ten flow loops, the effect of dimensionless pipeline length on severe slugging frequency was analyzed and an empirical correlation was developed to predict severe slugging frequency. Good matches with literature data demonstrated the validation of the empirical correlation. The severe slugging frequency correlation was applied to predict severe slugging length and derive a new transition criterion between classical severe slugging and transitional severe slugging in the flow pattern map.

      PubDate: 2018-04-16T08:42:27Z
       
  • Hydrodynamics and bubble size in bubble columns: Effects of contaminants
           and spargers
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): L. Gemello, C. Plais, F. Augier, A. Cloupet, D.L. Marchisio
      The simulation of bubble columns operating under the heterogeneous regime is an ambitious challenge, due to the difficulty of predicting accurately hydrodynamics and bubble size distributions, that requires experimental data for model validation. Gas fraction distributions, liquid and gas velocity profiles and bubble size distributions across bubble columns are deeply interconnected in these systems and only a comprehensive study allows the links between them to be understood. This work reports experimental data obtained by measuring bubble sizes with an innovative technique based on the cross correlation between two optical probes. Particular attention is given to the role of additives and impurities with a view to suppressing bubble coalescence. Initially experiments are carried out with demineralized water; subsequently they are repeated with tap water and adding small quantities of ethanol. Results show that contaminants and alcohol addition suppress bubble coalescence and induces a decrease of mean bubble sizes. Furthermore, alcohol addition delays the transition from homogeneous to heterogeneous regimes and increases the gas hold-up under the heterogeneous regime. Gas distribution is studied through two different perforated spargers. Changing the sparger it is possible to modify the bubble size in the lowest part of the column significantly. A perforated sparger with big holes causes the formation of big bubbles close to the holes of the sparger and promotes bubble breakage in the lower part of the column. By combining ethanol addition and sparger modification, bubble coalescence and bubble breakage can be decoupled in a controlled manner and interesting conclusions concerning these processes can be drawn. Beyond the novelty of bubble size measurements at high gas fraction, the experimental data collected are very useful to validate and develop computational fluid dynamics simulations coupled with population balance models suitable for heterogeneous bubbly flows.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Beyond the standard two-film theory: Computational fluid dynamics
           simulations for carbon dioxide capture in a wetted wall column
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Chao Wang, Zhijie Xu, Canhai Lai, Xin Sun
      The standard two-film theory (STFT) is a diffusion-based mechanism that can be used to describe gas mass transfer across liquid film. Fundamental assumptions of the STFT impose serious limitations on its ability to predict mass transfer coefficients. To better understand gas absorption across liquid film in practical situations, a multiphase computational fluid dynamics (CFD) model fully equipped with mass transport and chemistry capabilities has been developed for solvent-based carbon dioxide (CO2) capture to predict the CO2 mass transfer coefficient in a wetted wall column. The hydrodynamics is modeled using a volume of fluid method, and the diffusive and reactive mass transfer between the two phases is modeled by adopting a one-fluid formulation. We demonstrate that the proposed CFD model can naturally account for the influence of many important factors on the overall mass transfer that cannot be quantitatively explained by the STFT, such as the local variation in fluid velocities and properties, flow instabilities, and complex geometries. The CFD model also can predict the local mass transfer coefficient variation along the column height, which the STFT typically does not consider.

      PubDate: 2018-04-16T08:42:27Z
       
  • Hydrodynamics and mass transfer in an internal airlift slurry reactor for
           process intensification
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Tao Yang, Shujun Geng, Chao Yang, Qingshan Huang
      By combining the prominent advantage of directional fluid flow in an internal airlift loop reactor with the cheap cost of liquid-solid separation in a hydrocyclone, a new slurry reactor for process intensification integrating solid catalytic reactions with liquid-solid separation for clear liquid products is proposed and designed to cut down the capital and operating costs. The reactor can be operated properly when the superficial gas velocity is above 0.0108 m/s, and the solid particles of aluminum oxide are all retained in the slurry reactor if the particle diameter is larger than 57.9 μm. The influences of superficial gas velocity and top clearance on the performance of hydrodynamics and mass transfer in the gas-liquid two-phase and the gas-liquid-solid three-phase systems are measured and discussed systematically, and some data base for the rational design, optimization and scaling-up of this type of promising reactor is provided.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Numerical modeling of analyte diffusion and adsorption behavior in
           microparticle and nanoparticle based biosensors
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Ashley J. Driscoll, Patrick A. Johnson
      Increasingly medical diagnostic platforms rely upon the use of colloidal nanoparticles for the detection of biomolecules. Colloids offer greatly increased surface area to volume ratios and lack diffusion limitations that typically reduce reaction rates in assays employing planar surfaces. These characteristics are anticipated to improve the speed to answer as well as the total number of analytes that are captured in colloidal assay systems. This paper details a reaction-diffusion modeling approach to optimize colloidal affinity-based bioassays, with emphasis on the key figures of merit of projected sensitivities and time to answer over a broad range of conditions. The computational results illustrate the intuitive sense that colloidal sensing surfaces have improved kinetics as compared to solid supports, that the curvature of the spherical sensing surface probes a larger volume than a planar surface of the same area resulting in a larger diffusional driving force for reaction to the surface and equilibrium of bound analyte. The governing regime of particle systems skewed toward kinetically limited regimes and multiple configurations of particle diameter and concentration achieved equivalent analyte capture. Surface based sensor platforms have benefited from miniaturization of the capture area and particle capture systems provide a route to further surface miniaturization, as well as unique opportunities for the rapid analysis of dilute samples of particular interest for point-of-care (POC) diagnostics.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Prediction of species concentration distribution using a rigorous
           turbulent mass diffusivity model for bubble column reactor simulation part
           I: Application to chemisorption process of CO2 into NaOH solution
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Chao Zhang, Xigang Yuan, Yiqing Luo, Guocong Yu
      Rigorous prediction of species concentration distribution has been challenging in the simulation of bubble column reactors. In the present manuscript, a theoretical model of turbulent mass transfer is introduced to the numerical simulation of the process of chemisorption of CO2 into NaOH aqueous solution in a bubble column reactor. In this model the turbulent mass diffusivity was expressed as a function of the concentration variance c 2 ‾ and its dissipation rate ε c , which were modeled to close the turbulent mass transfer differential equation system. As a result, along with the fluid velocity distribution, the species concentration distribution in the bubble column can be rigorously predicted simultaneously. By using the present model, the experience relying assumption of a constant turbulent Schmidt, which has been usually adopted in a traditional species concentration simulation, can be avoided. An RNG k-ε method combined with a population balance model for predicting the bubble size distribution was used to predict the gas–liquid velocity in the turbulent flow. The simulated pH values and carbonate concentration were shown to be in satisfactory agreement with the experimental data in literature. The simulations showed that the turbulent mass diffusivity varied along axial and radial directions in the bubble column and the calculated turbulent Schmidt number was not a constant. The proposed approach can be especially useful when empirical turbulent mass diffusivity is not available for simulating a similar process in a bubble column reactor.

      PubDate: 2018-04-16T08:42:27Z
       
  • Reform of the drift-flux model of multiphase flow in pipes, wellbores, and
           reactor vessels
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Damon E. Turney, Dinesh V. Kalaga, Manizheh Ansari, Roman Yakobov, J.B. Joshi
      To aid the understanding of multiphase flows and development of associated computational simulations, we reappraise the drift-flux model to improve accuracy and physical understanding. New insights are supported by careful re-derivation, literature review, and empirical verification. We directly calculate C 0 and C 1 using simultaneous measurements of instantaneous gas fraction and gas-liquid velocities, all obtained from a microscopic measurement volume (∼1 mm3) inside a macroscopic gas-liquid pipe flow (∼5000 cm3) containing bubbles of ~250 μm diameter. A reformulated drift-flux plot is created for this macroscopic flow by using γ-beam densitometry and total flow measurements. The microscopic and macroscopic data both confirm that significant error exists in common methods and assumptions regarding the drift-flux model, namely in the common assumption that the drift-flux parameters C 0 and C 1 are invariant with respect to changes of flow. Our reformulated drift-flux model finds greatly different values of C 0 and C 1 from those predicted by standard drift flux methods, and finds values of C 0 and C 1 to undergo a regime transition due to changing bubble dynamics in the multiphase flow, wherein at low gas flow the bubbles seldom interact, as if they are at infinite dilution, while above a critical gas flow the hydrodynamics change due to bubbles interacting significantly with each other. These insights are uncovered only by reformulation of the practices of the drift-flux model.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Pulsatile electroosmotic flow in a microchannel with asymmetric wall zeta
           potentials and its effect on mass transport enhancement and mixing
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): I. Medina, M. Toledo, F. Méndez, O. Bautista
      In this work, we analyze theoretically the mass transport of a neutral solute in a pulsatile electroosmotic flow (PEOF), circulating in a parallel flat plate microchannel whose walls are characterized by asymmetric zeta potentials. The microchannel is connected to a two reservoirs having different concentrations. To analyze the mass transport in the PEOF, the Debye-Hückel approximation is assumed, and the electric potential in the Debye length is obtained from the Poisson-Boltzmann equation. Then, using the momentum and concentration equations, the flow and concentration fields are analytically determined for the periodic stage. Such field distributions depend principally on three dimensionless parameters: an angular Reynolds number, the Schmidt number, and the ratio between the half height of the channel and the Debye length. For obtaining insight on the physical aspects of the studied phenomenon, an asymptotic solution is additionally obtained in the limits of small and large values of the angular Reynolds number. Some important results derived from this analysis show the conditions for which the mass transport of a neutral solute can be enhanced and the circumstances whereby mixing of species is achieved.

      PubDate: 2018-04-16T08:42:27Z
       
  • Fluid-structure interaction using lattice Boltzmann method: Moving
           boundary treatment and discussion of compressible effect
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Wei Tan, Hao Wu, Guorui Zhu
      We investigate fluid-structure interaction using lattice Boltzmann method (LBM), where we introduce a new simple treatment for moving boundary. Sub-grids are defined to separate structures from main-grid, thus structures can be created and calculated independently. Mapping and interpolation are used to connect main-grid and sub-grids. Our proposed simulation approach demonstrates high reliability and stability when compared to the direct bounce back method available in the literature. We validate the proposed approach by simulations of a single vibration cylinder in still water and in flowing water. The results show good agreement with theory and reference experiments. We find a delay of fluid force in the simulation of compact cylinder array, and conclude that Mach number (Ma) and boundary force term have a great influence on the accuracy of calculation results. Ma should be carefully chosen for a reliable result. Compressible effect in LBM and its influence on calculation of fluid-structure interaction, which has not been studied in detail, are also discussed in this paper. It is hard to avoid time delay effect under the framework of LBM according to the analysis, and this may lead to inaccurate results in fluid-structure interaction calculation using LBM under certain conditions, which deserve more attention. This paper investigates the vibration of structure in fluid using LBM, which will support the research for fluid induced vibration.

      PubDate: 2018-04-16T08:42:27Z
       
  • A multiscale model for carbon adsorption of BTX compounds: Comparison of
           volume averaging theory and experimental measurements
    • Abstract: Publication date: 20 July 2018
      Source:Chemical Engineering Science, Volume 184
      Author(s): Cleuzir da Luz, Selene Maria de Arruda Guelli Ulson de Souza, Antonio Augusto Ulson de Souza, Adriana Dervanoski, Antonio de Oliveira Samel Moraes, Brian D. Wood
      In this work, the method of volume averaging is applied for the mathematical modeling of transport and adsorption of benzene, toluene, and xylene in a packed bed of activated particles. One benefit of this approach is that it allows one to directly incorporate measured microscale information into macroscale models for predicting the effective transport and adsorption process. This work is novel in that it combines two levels of upscaling and a nonlinear adsorption process. The first level of upscaling develops an effective model for the mass transport and reaction in an activated carbon particle; within the particle, only diffusion and reaction are considered because of the very small pore sizes. The second level of upscaling develops the effective model for a collection of carbon particles forming the porous medium contained in a fixed-bed reactor; here, convection, diffusion, and dispersion are considered. The resulting model resembles a classical mobile-immobile representation of the transport and adsorption process. As part of the upscaling process, we develop the homogenized transport equations and their associated effective parameters using two different averaging volume support scales (i.e., at two disparate length scales). The effective parameters are all diffusion or dispersion tensors. These include (1) the effective diffusion tensor defining diffusion in the homogenized carbon particle, (2) the effective diffusion tensor for the immobile phase in the two-region representation of the medium, and (3) the effective hydrodynamic dispersion tensor (which included diffusion and dispersion) for the mobile region of the porous catalyst bed. Each of these effective parameters are determined by numerically solving closure problems over an idealized spatially periodic model of a porous medium. One novel feature of these particular closure problems is that they describe nonlinear adsorption at the microscale, which is a problem that is not currently represented in the literature. Once derived, the two-scale, two-equation mobile-immobile model was applied to predict experimentally-measured concentration breakthrough curves from packed bed columns with activated carbon from coconut shell as the adsorbent to the removal of petrochemical contaminants (BTX) by adsorption. There were no adjustable parameters in this modeling effort; the only modeling choice was whether the mass transfer coefficient should be computed from the correlations of Wakao and Funazkri (1978) for BTX components. The equations from closure problems and Darcy’s scale of transport of this work were discretized using the finite volumes method and the solutions are found numerically through of a computational code and some packages from the free software OpenFOAM®, version 2.2.x. This work has been selected by the Editors as a Featured Cover Article for this issue.

      PubDate: 2018-04-16T08:42:27Z
       
  • Strategies for improving nitrogen removal under high sludge loading rate
           in an anammox membrane bioreactor operated at 25 °C
    • Abstract: Publication date: 29 June 2018
      Source:Chemical Engineering Science, Volume 183
      Author(s): Shaohua Sun, Ying Song, Xiao Jin Yang, Hanjun Hu, Shangze Wu, Wei-kang Qi, Yu-You Li
      An anaerobic ammonium oxidation (anammox) membrane bioreactor operated at 25 °C was used to investigate nitrogen removal under different operation conditions, namely, different sludge retention time (SRT) and nitrogen loading rate (NLR). The inhibition processes caused by high substance concentrations and over-loading were able to be circumvented by various adjustment methods. Furthermore, specific anammox activity (SAA) tests were performed to evaluate the effects of ammonium and nitrite on the anammox sludge. Over an SRT of 500 d, the content of volatile suspended solids (VSS) gradually increased from 125 mg/L to 5590 mg/L, and the maximum nitrogen removal rate (NRR) reached 1.18 kg N/m3/d. When the SRT was decreased to 50 d, the sludge concentration declined gradually, which necessitated an increase in the sludge loading rate (SLR), and the maximum sludge nitrogen removal rate (SNRR) of 0.67 g total nitrogen (TN)/g VSS/d was achieved at this time.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Modeling of local maskless electrochemical deposition of metal
           microcolumns
    • Abstract: Publication date: 29 June 2018
      Source:Chemical Engineering Science, Volume 183
      Author(s): V.M. Volgin, T.B. Kabanova, A.D. Davydov
      The work deals with the problem of fabricating new materials for modern devices of microelectromechanics, microelectronics, biomimetics, etc. using the local electrodeposition of metals. The mathematical model is developed for the formation of 3D microstructures (microcolumns) by the local electrochemical deposition of metal using a moving disk microanode. The numerical solution of the mathematical problem is performed using the finite element method on the irregular grid. The grid is deformed and adaptively remeshed during modeling of deposit growth. Evolution of deposit surface is calculated for various exchange current densities, transfer coefficients, interelectrode distances and various dependences of the current efficiency on the current density. The results of modeling allow one to determine the relationships between the parameters of electrodeposition and the shape and dimensions of formed microstructures. These data can be used to predict the results of local electrodeposition of metal and to optimize the operation conditions.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Engineering embolic microparticles from a periodically-pulsating charged
           liquid meniscus
    • Abstract: Publication date: 29 June 2018
      Source:Chemical Engineering Science, Volume 183
      Author(s): Xiaowei Tian, Tiantian Kong, Pingan Zhu, Zhanxiao Kang, Leyan Lei, Xin Tang, Liqiu Wang
      A commercial-scale generation of uniform and well-controlled soft microparticles is critical for therapeutic embolization, a minimally invasive, nonsurgical interventional therapeutic technique for the treatment of various conditions, including tumors, vascular lesions and hemorrhages. We report the generation of required embolic microparticles from an electrified meniscus of the precursor alginate solution. A micro-dripping regime is identified with electric Bond number BE being from 0.3 to 1 and Weber number We < 1, where the conical tip of the charged meniscus emits a single yet fine droplet periodically. The droplet diameter dd and its generation frequency f scale with the dimensionless controlling parameters in the form of d d ∼ q 0.5 , f ∼ q - 0.15 B E 0.67 in this regime, with q being the dimensionless flow rate. Our results are valuable for effective production of therapeutic microparticles on a commercial scale from precursor solution of similar physical properties.

      PubDate: 2018-04-16T08:42:27Z
       
  • Reconstruction method for temperature field measurement using ultrasonic
           tomography
    • Abstract: Publication date: 29 June 2018
      Source:Chemical Engineering Science, Volume 183
      Author(s): S.Y. Ren, J. Lei, Z.P. Jia
      The gas temperature field measurement is crucial for the monitoring of the objects of interest. Owing to the distinct advantages, including non-invasive sensing, high safety, etc., the ultrasonic tomography (UT) method is considered to be a promising visualization measurement method, in which acquiring high-quality images is vital for real-world applications. In this paper, a new UT measurement system that integrates the Data Acquisition Card and a Single Chip Microcomputer is proposed for the temperature distribution measurement. A hardware system is designed to alleviate the inertia delay phenomenon. A reconstruction model that simultaneously emphasizes the inaccurate properties on the reconstruction model and the measurement data is proposed. By means of introducing the radial basis function method and the framework of the Tikhonov regularization technique, a two-stage reconstruction method is proposed to alleviate the ill-posed nature in the UT inverse problem. A new objective functional is proposed to convert the original reconstruction task into an optimization problem, and the simulated annealing algorithm is deployed to effectively solve the proposed objective functional. Experimental results validate the feasibility and effectiveness of the proposed reconstruction method.

      PubDate: 2018-04-16T08:42:27Z
       
  • Heterogeneous oxidation of zinc vapor by steam and mixtures of steam and
           carbon dioxide
    • Abstract: Publication date: 29 June 2018
      Source:Chemical Engineering Science, Volume 183
      Author(s): Luke J. Venstrom, Paul Hilsen, Jane H. Davidson
      The kinetics of the heterogeneous oxidation of zinc vapor by water vapor were measured in a tube flow reactor for temperatures from 800 to 1100 K, zinc vapor partial pressures up to 0.39 atm, and water vapor partial pressures up to 1.0 atm. The results extend the prior data for oxidation of zinc by water vapor from zinc partial pressures on the order of 0.01 atm to higher values appropriate for fuel production via the Zn/ZnO thermochemical cycle. Measured oxidation rates span 10−7–10−5 mol cm−2 s−1. A second order, reversible reaction rate expression r ″ = k Zn - H 2 O p Zn ( g ) p H 2 O - p H 2 K eq is developed from regression of the data and a numerical model of advective and diffusive mass transfer. The kinetic parameter k Zn - H 2 O is a non-monotonic function of temperature with a negative activation energy for temperatures between 800 and 1050 K, consistent with prior studies. In a second set of experiments, the rate of the heterogeneous oxidation of zinc vapor by mixtures of water vapor and carbon dioxide was measured. The product gas is hydrogen rich due to faster surface reaction kinetics for oxidation with water vapor than with carbon dioxide. We conclude that it is preferable to split water and carbon dioxide in separate reactors rather than co-produce H2 and CO in a single reactor for production of synthesis gas in the Zn/ZnO solar thermochemical redox cycle.

      PubDate: 2018-04-16T08:42:27Z
       
  • Photocatalytic degradation of Orange G using sepiolite-TiO2
           nanocomposites: Optimization of physicochemical parameters and kinetics
           studies
    • Abstract: Publication date: 29 June 2018
      Source:Chemical Engineering Science, Volume 183
      Author(s): Feng Zhou, Chunjie Yan, Tian Liang, Qi Sun, Hongquan Wang
      Highly photoactive nanocomposites Sep-TiO2 with various ratios of Ti/Sep were prepared by a novel microwave-hydrothermal method and were compared for their photocatalytic activity. The catalyst with the Ti/Sep ratio of 40 mmol/g showed the highest photodegradation activity on account of its relatively intact sepiolite structure and more anatase active sites. The effects of operational conditions, including photocatalyst amount, initial dye concentration and pH on photocatalytic degradation performance were analyzed and optimized, which demonstrated low and negligible photodegradation efficiency in the presence of sepiolite only and in the absence of photocatalyst, respectively. The photocatalytic degradation kinetics under different reaction conditions was elucidated by modeling. The results showed that the photocatalytic degradation of Orange G could be described by the modified Langmuir-Hinshelwood model. The photocatalytic degradation process fits into first-order kinetics for most of the operational parameters, while follows zero-order kinetics for the condition of high dye concentration. The apparent rate constants kapp for each degradation reaction were calculated by fitting the model to experimental data and the highest value was obtained at catalyst dosage 0.8 g/L, initial dye concentration 10 mg/L and pH = 3. Moreover, the recycling experiments confirmed the stability of the catalyst.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Highly efficient and selective production of acrylic acid from
           3-hydroxypropionic acid over acidic heterogeneous catalysts
    • Abstract: Publication date: 29 June 2018
      Source:Chemical Engineering Science, Volume 183
      Author(s): Chao Li, Qiangqiang Zhu, Ziheng Cui, Bin Wang, Yunming Fang, Tianwei Tan
      The process for dehydration of 3-hydroxypropionic acid to produce acrylic acid was investigated over solid acid catalysts containing HY, ZSM-5, Beta, MCM-41 and silica gel. These catalysts were comprehensively characterized by techniques including XRD, nitrogen adsorption–desorption, NH3-TPD, Pyridine-IR, TGA and 13C CP MAS-NMR. Silica gel was found to show the highest acrylic acid selectivity of >99.0% at a complete 3-hydroxypropionic acid conversion. Results from NH3-TPD and Pyridine-IR analyses reveal that the acidity has a significant effect on catalytic performance. The selective conversion of 3-hydroxypropionic acid to acrylic acid over silica gel can be ascribed to the weak and small amount of Lewis acid sites as well as the absence of Brønsted acid sites. Increasing Brønsted acid sites for HY, ZSM-5, Beta and MCM-41 resulted in low acrylic acid selectivities due to increasing of acetic acid formation. TG and 13C CP MAS-NMR results further indicate that the presence of Brønsted acid sites favors the formation of coke. And the coke deposited on these catalysts has a primarily aromatic nature. Stability test indicates the silica gel catalyst exhibits an excellent stability for 200 h.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Optimization under uncertainty in chemical engineering: Comparative
           evaluation of unscented transformation methods and cubature rules
    • Abstract: Publication date: 29 June 2018
      Source:Chemical Engineering Science, Volume 183
      Author(s): Johannes Maußner, Hannsjörg Freund
      Model-based optimization under consideration of uncertainty is an important and active research topic. In order to handle uncertain model and process parameters for the design and optimization of chemical processes, various different approaches have been proposed in the literature. Among these approaches, the application of unscented transformation (UT) methods received increasing attention recently. The UT is used to calculate approximations of the first two statistical moments of the objective and constraints which are implemented in the optimization problem. Since the UT only allows for approximations of the statistical moments, the approximation error inevitably influences the optimization. In the present contribution, we emphasize that a poor approximation significantly reduces the meaningfulness of an optimization under uncertainty approach. Hence, we compare a variety of UT methods and study the effect of their corresponding tuning parameters on the approximation accuracy. Furthermore, we investigate four different cubature rules which are well known from the numerical integration literature and which show similarities to the UT from an implementational point of view. The individual methods are compared in terms of approximation accuracy and computational effort based on examples from chemical reaction engineering. Our results indicate that the cubature rule labeled as CU51 provides the most accurate results at reasonable computational costs. The recently proposed cubature rule labeled as MSSRC provides less accurate results, but is computationally more efficient than the CU51 rule and is thus an attractive alternative. Regarding the UT methods, the results show that the proper choice of the tuning parameter significantly influences the optimization results. Furthermore, it is shown that the common tuning parameter selection rule for the original UT does not necessarily yield the most accurate approximation. Hence, based on our results we suggest to favor the application of cubature rules for optimization under uncertainty over the unscented transformation methods.
      Graphical abstract image

      PubDate: 2018-04-16T08:42:27Z
       
  • Steady vs unsteady membrane gas separation processes
    • Abstract: Publication date: 29 June 2018
      Source:Chemical Engineering Science, Volume 183
      Author(s): Christophe Castel, Lei Wang, Jean Pierre Corriou, Eric Favre
      Nowadays, membrane processes are together with cryogeny, absorption and adsorption considered to be a key technology for gas separation applications. Process selectivity is of primary importance in order to respect the specifications but can in some cases be limited due to a too low membrane selectivity. Parallel to improvements in the membrane selectivity of certain materials, unsteady membrane operations can also be attempted in order to achieve a higher separation selectivity, but this strategy remains largely unexplored. A novel, simple, unsteady-state process, complementary to the strategies already proposed by the previous authors, is reported in this study. A systematic comparison of steady state, short-class (i.e. with time lag) and long-class (i.e. pseudo steady-state) processes is described for O2/N2 (PPO membrane), He/Kr (PEMA membrane) and H2/CO2 (polyimide and a reverse selective PEBAX membrane) separations. Based on a selectivity composition path chart, the maximal purity or process selectivity achievable by steady and unsteady processes was compared. The new long-class process was shown to offer similar or increased selectivity compared to steady-state operation, at the expense of a lower productivity. Finally, the applicability to industrial separations and the remaining challenges are also discussed.

      PubDate: 2018-04-16T08:42:27Z
       
 
 
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